Jennifer Lopez returned to her old New York City neighbourhood on Sunday to urge residents to follow her healthy eating campaign.

The star teamed up with health experts at the Montefiore Medical Center last month to promote a better understanding of nutrition in the Bronx, which is struggling with a childhood obesity epidemic.

She shocked locals who had turned out at the medical facility's Norwood campus, before explaining that she had found it daunting to switch from eating a meat and carbohydrate heavy diet to veganism.

Lopez explained, "I grew up on rice and beans and pork chops... (Change is) scary... But all it means is making grains and fruits and vegetables the main part of every meal we make."

The mother-of-two also vowed to help bring down the official rate of overweight children in the borough, which is currently at 50%.

She added, "I'm not having that! No. This has to change. We have to start doing good things for ourselves now."

Lopez's visit comes amid growing calls from many locals in the Bronx's City Island for officials to step in and cancel her free concert at Pelham Bay Park on Wednesday over fears the roads will come to a standstill with extra traffic.